Central heating queries

arkonite_babe

We have moved into our new home and discovered central heating boiler badly rusting and perforated. Radiators are showing similar signs of corrosion, we have replaced the boiler, flushed the system and added inhibitor to the system.

Question? What may have been the cause of the corrosion and how do we prevent reoccurence?

Thanks

Edited to add: As far as we can find out, the bolier was installed in the house 7 to 8 years ago. Approx 1997/1998

ManAtHome

Worth a read http://www.plumbingpages.com/featurepages/GenericSolutions.cfm Surprised it's gone that quickly, may be the alkaline water thing (either that or they must have had bubbly/bangy pipes for a long time).

budgetflyer

Could be a water leak under floor. This would cause system to constantly top up and speed up corrosion process.
I might add, there are some rubbish makes out there. With our constant strive to get things cheaper and cheaper some manufacturers are reducing quality to compete on price only.

arkonite_babe

We have no evidence of any leaks under floor. Solid floors, so no way to tell!

IJJoseph

There are several things that can cause it but I suspect that the previous owners never had the system serviced.

Once a year the system should be drained, refilled and inhibitor added.

I hope when the new boiler was installed the system was flushed to ensure that any muck was removed.

Flushing should be relatively straightforward. Just add Flushex or Fernox System Restorer. Leave it for a week (or longer if it really needs it - but no longer than 21 days!) and run the central heating. Then drain the system down. Refill it and add inhinitor.

If you drain down the system and then refill it, adding inhibitor each year then corrosion should not occur.

CReWdog

Hi

You've done the right thing replacing the boiler, next you need some new radiators. Don't be tempted to think that by adding inhibitor now you have cured an already bad problem. You haven't, you've only delayed the point where the radiators will start to leak. Once things start going rusty adding ANY sort of inhibitor will not stop the corrosion entirely, only slow it down. Bite the bullet & change the rads before you end up with a flood.
As to the overall cause, well basically you have an chemical reaction going on inside your heating system, this is caused by a combination of the water in your system (how acidic or alkiline it is) & the dissimular metals used (copper pipes, iron in the boiler). The reaction occurs faster when everything is hot, the inhibitor you put in the system slows this reaction down but does not stop it entirely, you need to drain the system down every couple of yeasr & add new inhibitor.
If your water is REALLY hard or acidic it might be worth your while to use water that has been filtered, ok, this would take a while, but it would be worth it.
Just for the sake of stiring the pot, what did the survey say before you bought the house? You DID have one done, right???

Regards

CReWdog

c_smith

I wouldn't drain the water down every year or two years as suggested. Each time you add fresh oxygenated water to your system, you are speeding up the corrosion process. As the corrosion inhibiting qualities of the inhibitor weakens over time, it is advisable to add a carton of inhibitor roughly every two years to the existing water in the system without draining down.

Assuming you have a combi boiler, you should monitor the pressure in the system and ensure that you do not need to top it up with water regularly. If you do, then you have a leak somewhere which will require attention. A 0.1 - 0.3 bar pressure loss a couple of times a year is nothing to worry about.

Lastly, if any of the radiators are showing serious signs of corrosion, then given that you have went to the expense of fitting a new boiler, it would be advisable to replace them. You don't want flakes of corroded metal breaking off from inside badly corroded radiators and floating around your system and into your new boiler.

arkonite_babe

We have now replaced almost all of the radiators. Three to go!! Thanks all for your replies and I hope that this is our problems solved

calleyw

c_smith wrote:

I wouldn't drain the water down every year or two years as suggested. Each time you add fresh oxygenated water to your system, you are speeding up the corrosion process. As the corrosion inhibiting qualities of the inhibitor weakens over time, it is advisable to add a carton of inhibitor roughly every two years to the existing water in the system without draining down.

Interesting we have just had a new boiler and rads put in as well as tapping in to the old system.

And they told us that new inhibitor was only needed about once every 5 years if you don't drain the system down.


Yours


Calley